I want to backtest a long term strategy trading HYG (high yield bond ETF). However, HYG's history is too short for backtesting. I am looking for a long term proxy for HYG, such as a high yield bond mutual fund, but I can't find any good ones that have similar performance like HYG. Most funds, such as VWEHX, perform quite differently than HYG and usually outperform HYG by a large margin over the long term. Does anyone know any high yield bond fund that exists for a long time and closely tracks the performance of HYG? Thanks.